diff --git a/doc/91_relnotes.qbk b/doc/91_relnotes.qbk
index 8db03b0..e63e299 100644
--- a/doc/91_relnotes.qbk
+++ b/doc/91_relnotes.qbk
@@ -13,7 +13,7 @@
 
 [heading Boost Release 1.80]
 
-* Added specializations for `std::hash<boost::opitonal<T>>`. This fixes [@https://github.com/boostorg/optional/issues/55 issue #55].
+* [*Breaking change:] Added specializations for `std::hash<boost::opitonal<T>>`. This fixes [@https://github.com/boostorg/optional/issues/55 issue #55]. You may get compiler errors when your program provides specializations for `std::hash<boost::optional<T>>`. If this happens, define macro `BOOST_OPTIONAL_CONFIG_DO_NOT_SPECIALIZE_STD_HASH` to suppress the specializations of `std::hash` in this library.
 
 [heading Boost Release 1.79]